Outline Specification
Crew: 8
Commander
1 driver
6 gunners
Armament
Male: 2 x 6-pdr 23 cal. Hotchkiss QF, 4 Hotchkiss MG
Female: 6 Hotchkiss MG
Engine
Ricardo 6-cyl. ‘vertical’ 150hp
hp per ton: 5.2hp
Est’d endurance: 10 hrs
Max speed: 4.6mph on level
Transmission
4-speed forward and 4-speed reverse
Epicyclic gear in final drive to each track, in permanent mesh
Dimensions
Length: 26ft 5in
Male width: 13ft 6in
Female width: 10ft 6in
Height: 8ft 8in
Track width: 20.5in
Fighting weight etc.
Male: 29 tons
Female: 28 tons
Max trench crossing: 10ft
Mk V Star Heavy Tank
The Allies were aware in late 1917 that the Germans were widening their trenches against tanks. Attempts were made to lengthen Mk IV and V tanks by the rearward extension of their track frames. ‘Tadpole tails’ were made up in mild steel to replace existing rear horns, but the 9ft tails lacked lateral rigidity and whipped when the tank turned in spite of extra cross bracing. Tank Corps Central Workshops in France were first to attempt the alternative of cutting a Mk IV in two and inserting extension frame members and armour. At home the Mechanical Warfare Department at the Ministry of Munitions then cut and shut a Mk V just behind the sponsons after inserting a 6ft extension. This boosted trench-crossing capability from 10ft to 13ft in width, and avoided recourse to giant drum-like fascines which had earlier been roofmounted for release into the enemy trench as a bridging device. The enlarged fighting compartment was an added bonus. The rear turret’s previously vertical end plates were sloped to allow greater elevation of its machine guns. In other respects the Star was generally the same as Mk V.
Origination
Design began: c. November 1917
Designed by: Maj W.G. Wilson
Sole builder: Metropolitan Carriage, Wagon & Finance Co. Ltd
First series production tank completed: female on 11 May and male on 1 July 1918
First trials
20.4.18. Brief tests by Metro on preproduction machine. No long-distance trials for this mark
WD serial numbers
Male: 9501–9700 and 10001–10300
Female: 9751–9950
Experimental: 9501, 9752, 9865
Outline Specification
Crew: 8
Commander
1 driver
6 gunners
Armament
Male: 2 x 6-pdr 23 cal. Hotchkiss QF, 4 Hotchkiss MG
Female: 6 Hotchkiss MG
Engine
Ricardo 6-cyl. ‘vertical’ 150hp
hp per ton: 4.28hp
Est’d endurance: 9.5 hrs
Max speed: 4.6mph on level
Transmission
4-speed forward and 4-speed reverse Epicyclic gear in final drive to each track, in permanent mesh
Dimensions
Length: 32ft 5in
Male width: 13ft 6in
Female width: 10ft 6in
Height: 8ft 8in
Track width: 20.5in
Fighting weight etc.
Male: 33 tons
Female: 32 tons
Max trench crossing: 13ft
Mk V Two Star Heavy Tank
The Mk V Star was still on the drawing board on 11 January 1918 when the War Office considered ordering an initial 300 of the big Anglo-American Mk VIII tanks to follow it. News of a delay in securing release of the US-built Liberty engines for them led the army to decide instead to order 300 of an uprated Mk V Star with a more powerful Ricardo engine. The resultant Mk V Two Star machines were to be 50/50 Male/Female, to complete delivery by 15 November 1918. They were the same length and width as the Star but track contour was altered with a greater camber on the lower run to improve manoeuvrability. Wider 26.5in track shoes were fitted. The engine in the earlier ‘V’ series was retained but its cylinders were bored out to develop 225hp. It was also located further back so that the fighting chamber lay largely ahead of it instead of around it. The commander’s turret was enlarged and moved right up to the driver’s to form one space. Metropolitan built all 1,125 tanks in the ‘V’ series, including 25 Two Star machines.
Origination
Design began: January/February 1918
Designed by: Maj W.G. Wilson
Sole builder: Metropolitan Carriage, Wagon & Finance Co. Ltd
First series production tank completed: December 1918
First trials
Late November 1918. Manoeuvred very well in first run
WD serial numbers
Male: 10501–10650 and 10901–11500
Female: 10701–10850
Experimental: 10704 (F) for bridging and mine clearance research
Outline Specification
Crew: 8
Commander
1 driver
6 gunners
Armament
Male: 2 x 6-pdr 23 cal. Hotchkiss QF, 4 Hotchkiss MG
Female: 6 Hotchkiss MG
Engine
Ricardo 6-cyl. ‘vertical’ 225hp
hp per ton: 6.4hp
Est’d endurance: 12.9 hrs
Max speed: 5.2mph on level
Transmission
4-speed forward and 4-speed reverse
Epicyclic gear in final drive to each track, in permanent mesh
Dimensions
Length: 32ft 5in
Male width: 13ft 6in
Female width: 10ft 6in
Height: 9ft Track width: 26.5in
Fighting weight etc.
Male: 35 tons
Female: 34 tons
Max trench crossing: 13ft
Mk VII Heavy Tank
This machine was intended to provide better one-man steering and speed control with less driver fatigue and improved trench-crossing capability. The hull was essentially a stretched Mk V, 3ft 6in longer, and fitted with clutchless variable hydraulic gears, one set for each track. A similar Williams Janney transmission had been installed in a Mk III and tested against other systems on 3 March 1917 at Oldbury. Although it was rejected in favour of Maj Wilson’s epicyclic final drive, it was thought worth continuing to develop. That May 24 sets of hydraulic gears were ordered for a Mk VII to be built by Brown Brothers of Edinburgh, a Vickers subsidiary. The gears came from their sister company Variable Speed Gear Ltd. A Ricardo 150hp engine drove two VSG pumps coupled to a pair of hydraulic motors. Altering the pressure of the pumps produced infinitely variable speeds up to 4.25mph. As the two sets operated independently, power could be applied to either track through all forward and reverse speeds to give steering. There were separate radiators in the track frames for engine coolant and hydraulic oil. The two systems generated prodigious heat which was extracted from the engine compartment by twin 20in fans inducting and venting air through armoured roof grilles at 7,500cu ft per minute. Mk VII was one of the first tanks to be equipped with electric starting. A prototype was built and tested in October 1917 with promising results, followed in January by orders for a further 74. Kitson’s of Leeds were to share the work but their contract was later withdrawn to free capacity for locomotive construction. This was the only tank to be assembled by Brown’s, whose suppliers included Greenwood & Batley of Leeds for the epicyclics, and rail wagon builders Hurst Nelson of Motherwell for hulls at a scheduled three per week. The first hull reached Brown’s in May 1918 and only two more had arrived by the end of November, priority going instead to Medium C construction. Despite the Mk VII tank’s fine manoeuvrability and ease of operation, its transmission was costly, came with a weight penalty, and was technically complex. Its power-to-weight ratio was poor and the engine remained in a cramped fighting compartment. The first Mk V Two Star machines with their superior internal layout and p
erformance were ordered within days of Mk VII, followed soon afterwards by the even better Mk VIII. Thereafter the VII programme ran on ‘near-empty’.
Origination
Design began: November 1916
Designed by: Maj H. Knothe
Contributors: Lt O. Thorneycroft, Mr John Robson, Mr Hudd
Sole builder: Brown Brothers Ltd, Edinburgh
Prototype completed: October 1917
First series production tank completed: July 1918
First trials
November 1917. Promising results from prototype
July 1918. 90-mile trial run of first production machine; gearbox failed. In August a 400-mile trial with redesigned box was successfully completed
WD serial numbers
Brown: 5051–5088
(5051 was experimental)
Kitson: 5001–5036
Outline Specification
Crew: 8
Commander
1 driver
6 gunners
Armament
Male only: 2 x 6-pdr 23 cal. Hotchkiss QF, 4 Hotchkiss MG
Engine
Ricardo 6-cyl. ‘vertical’ 150hp
hp per ton: 4.54hp
Est’d endurance: 11.5 hrs
Max speed: 4.25mph on level
Transmission
Clutchless. Williams Janney hydraulic infinitely variable gear, 1 set to each track
Dimensions
Length: 29ft 10in
Width: 13ft 9in
Height: 8ft 7in
Track width: 26.5in
Fighting weight etc.
33 tons
Max trench crossing: 11ft 6in
Mk VIII Heavy Tank
The Mk VIII ‘Liberty’ or ‘International’ tank was co-designed by Britain and America primarily as a fighting vehicle but with troop carrier or supply tank capability. Variations in engines and details resulted in ‘British’ and ‘Liberty’ versions. Similar to the earlier tanks at a glance, it was in fact a completely new type taking the best of previous designs including Mk IX. 1,500 Liberty tanks were to be assembled in France. Britain would contribute hulls, guns, ammunition, track plates, rollers and instruments. The US would supply modified 300hp Liberty aero engines, transmissions and track parts. Larger-scale production in France and America was planned. At 37 tons and over 34ft long Mk VIII was the biggest and heaviest tank to date, its floor space allowing full bulkhead separation of the engine from the large fighting compartment in front. The 6-pdr guns were in doorless sponsons. Five machine guns had all-round fire from an 8ft long turret, as well as lateral arcs from mountings in the large side doors. Ground clearance at 1ft 9in was over 4in better than previous ‘heavies’, and track ground pressure was almost halved. To ensure the interchangeability of parts between Allied forces all jigs were made by one firm, the Leeds Forge Co.
The War Office considered ordering 300 British Mk VIII tanks in January 1918, but the supply of Liberty engines from the US was seriously delayed by the needs of their aircraft production, and there was fear of loss from U-boat activity. The order went to the Mk V Two Star instead. When 1,375 British Mk VIII machines were ordered in April, Harry Ricardo was asked to produce an engine for them comparable with the Liberty unit’s 300hp output. His power plant delivered 330hp. Mk VIII production was cut to a handful that September in preference for the faster and more easily mass-produced Medium C. The war had become one of pursuit. The contract for Britain’s contribution of 1,500 Liberty hulls had gone in March to a consortium led by Mr F.J. West, General Manager of West’s Gas Improvement Co. Ltd of Manchester. The group was not given the labour and materials priorities to enable it to start work until November. A British-made Mk VIII Liberty hull and its guns were shipped to America in June for completion – it was one of two hulls in mild steel built by West’s. America was in no position to start volume tank production in 1918, but the Ordnance Department purchased parts for 100 more Liberty machines after the war and assembled these at Rock Island Arsenal, completing in 1920.
Origination
Preliminary design begun August/September 1917 by: Lt G.J. Rackham
Formal design begun in December by:
US Army: Col Alden
Ministry of Munitions: Lt G.J. Rackham, Maj W.G. Wilson, Sir E.T. d’Eyncourt
Tank Corps: Lt Col Green
First builder: North British Locomotive Co. Ltd
Mock-up inspected: 11.1.18 2 mild steel prototypes were built by NB Loco, August and September 1918
First British series production tank completed by NB Loco, 18.10.18
2 mild steel Liberty hulls were ordered from West’s in April and delivered June 1918
First trials
August 1918: NB Loco prototype No. 1 was fitted for short trial runs with a Rolls
Royce 180hp engine pending delivery of the first Ricardo unit
10.9.18: NB Loco No. 1 demonstrated to Tank Board. Many defects. Transmission unsatisfactory even under 180hp loads. Epicyclic box covers broken twice in same place. Track fouling.
18.10.18: NB Loco prototype No. 2 was fitted with Ricardo 300hp V12 engine for full endurance trials at Newbury Tank Testing Station
23.10.18: Ricardo machine broke down completely with engine bearing trouble 20 miles into its 1,000-mile trial
30.11.18: no major problems but 1,000-mile trial still uncompleted
WD serial numbers
NB Loco: 12001–13040
Beardmore: 14001–14335
Outline Specification Capacity
Commander
1 driver
6 gunners
20 infantrymen
Armament
2 x 6-pdr 23 cal. Hotchkiss QF
Main turret: 5 Hotchkiss MG
2 side doors: 1 Hotchkiss MG in each
Engine
Ricardo V12, 300hp – or Liberty V12, 300hp
Engines interchangeable.
hp per ton: 8hp
Est’d endurance: 9.7 hrs
Max speed: 7mph on level
Transmission
A 2-speed compound epicyclic gear to each track giving two forward and reverse speeds, 1.4 and 5.2mph. The British type was designed to accept 4-speed gearing as a later option
Dimensions
Length: 34ft 2.5in
Width: 12ft 4in
Height: 10ft 3.5in
Track width: 26.5in
Fighting weight etc.
37 tons
Max trench crossing: 14ft
Mk IX Infantry Supply Tank
Mk IX was arguably the world’s first purpose-built tracked and armoured personnel carrier. Design by Lt George Rackham began in May 1917. A few months later he and Maj Wilson started to think about a fighting version (it eventually became Mk VIII) and much of Rackham’s structural innovation was common to both types. Interior space was maximized by severely cutting back the internal track frames which had been over-designed. The box-like hull of the Mk IX had no sponsons, its smooth flanks being carried out flush to the limits of the rail loading gauge. A Ricardo 150hp engine was up front with only the driver and commander ahead of it. To maximize load space the gearbox and epicyclics were set in the far rear, their control rods running back to the driver along the underside of the roof. The resulting area of some 13ft 6in by 7ft 7in, with 5ft 5in of uniform height, was clear save for the unshielded drive shaft which ran from front to back down the centre of the space at shin height. Claimed capacity was 30 men or 10 tons of stores. Two machines could carry between them a day’s supplies for an infantry brigade. But 30 troops laden with equipment in such a space would have suffered grievously. There were no seats or grab lines, and the swaying mass in the choking near-darkness was expected to stand clear of a rotating drive shaft. Two large oval doors on either side gave access.
Three machines reached France before the Armistice. When they got to Central Workshops it was found that the insides of the doors were painted white, no doubt to indicate their position in the interior gloom, but it brou
ght a strong complaint from the workshops office because if opened for evacuation under fire the bright door would have been a gift to gunners. A cargo tray covered much of the roof. Fixed armament comprised a forward-firing Hotchkiss MG beside the driver and another in the machine’s back plate covering its rear. Flank loopholes would enable passengers to use their small arms. In an attempt to improve ventilation, vanes were fitted to the enclosed flywheel to make it an extraction fan, drawing foul air from the interior and up through the sealed engine casing to discharge on the roof. Two or three prototypes in mild steel were built by Sir W.G. Armstrong, Whitworth & Co. One of them was sealed for flotation trials and fitted with pontoon cylinders strapped to the hull. A raised cab with extended exhausts was built in front, and hinged paddles were fitted to the tracks at intervals. A rear-mounted auxiliary motor gave propulsion. The ‘Duck’ was first launched on Armistice Day on London’s Welsh Harp lake near the tank experimental ground at Dollis Hill.
The Mk IX machine proved to be underpowered and prone to sink under load, whether on land or water. The army never got an effective all-terrain armoured carrier. It had been pressing the Mechanical Warfare Department for one since May 1917 and had called for 800 by mid-1918. Scarcity of materials and labour left auxiliary vehicle production well behind in the race to build more fighting types.
Origination
Design began: May 1917
Designed by: Lt G.J. Rackham supervised by Maj W.G. Wilson
Design completed: September 1917
First builder, prototypes: Sir W.G. Armstrong, Whitworth & Co.
Production machines: Wm Marshall Sons & Co.
Mock-up: inspected late September 1917 at Dollis Hill
First series production tank: delivered 8.6.18
First trials
January 1918. Prototype to Dollis Hill where driving chains broke repeatedly. Slow to steer due to greater track length in ground contact
WD serial numbers
901–1100
903, 907, 909 went to France late October
1918, the only Mk IX to get there before the Armistice
Outline Specification
Capacity
Commander
1 driver
2 machine-gunners
30 infantrymen or 10 tons of stores
The Devil's Chariots Page 37
